Post-mix beverage dispensing valves are well known in the art and are typically used to mix together two beverage constituents at a desired ratio to produce and dispense a finished drink. Such constituents generally consist of a concentrated syrup flavoring and diluent comprising carbonated or uncarbonated water. Various control strategies have been employed to maintain the desired syrup to water ratio. “Piston” type flow regulators are a well known purely mechanical system that employs spring tensioning of pistons that constantly adjust the size of orifice flow openings to maintain the desired ratio between the fluids. However, a failing with such systems is that they require both fluids to be held within relatively narrow flow rate windows in order to work effectively. As is well understood, differences in ambient temperature, syrup viscosity, water pressure and the like can all conspire to affect one or both of the flow rates to a degree that the drink is ratioed improperly becoming either too dilute or too concentrated. As a result thereof, a drink that is too sweet can waste syrup costing the retailer money, and whether too sweet or not sufficiently so, presents the drink in less than favorable conditions, also reflecting negatively on the retailer as well as the drink brand owner.
Volumetric piston dispense systems, as differentiated from the above piston based flow regulators, attempt to measure the volumes of each liquid using the known volume of a piston and the stroke thereof. Thus, two pistons, one for the syrup and one for the water are driven simultaneously by the same shaft or drive mechanism and are sized to reflect their desired volume ratio difference. Thus, operation of both pistons serves to move the desired volume ratio of each of the fluids from separate sources thereof to the dispense point or nozzle of the valve. However, these systems have met with difficulty in that there inherently exists a mechanical complexity relative to providing for inlet and outlet lines to each piston and providing for the correct timing of the opening and closing of such lines. Such complexity increases cost, imposes manufacturing difficulties and reduces operating reliability. Also, there exist size constraints that require the pistons to be relatively small resulting in high operating speeds that lead to corresponding seal and other mechanical wear issues, as well as undesired pumping phenomena where less than a full volume is moved with each pump stroke. Naturally, such wear and pumping inaccuracy problems can negatively impact the ratio accuracy.
Electronic post-mix valves are also known that utilize sensors for determining the flow rate of either the water, the syrup or both, and then, through the use of a micro-controller, adjust “on the fly” the flow rates of either or both of the water and syrup. In addition, hybrid systems are known that utilize both a volumetric piston approach for the syrup and a flow sensing of the water flow. However, such post-mix valves continue to be plagued with cost and reliability problems. The sensors, for example, can be both costly and unreliable. Thus, maintenance of such post-mix valves by trained service technicians remains a large part of the life cost thereof. In general, it appears that the ratioing technology employed in such electronic valves, while useful in large scale fluid ratioing applications, does not translate well into the relatively small size requirements required of such valves.
Accordingly, there is a great need for a post-mix valve that can accurately maintain the proper drink ratio consistently over time regardless of changes in temperature, flow rate and so forth and that is low in cost both as to the purchase price and the maintenance thereof.